SAPO-35 molecular sieve as well as synthesis method and application thereof

Abstract

The invention discloses an SAPO-35 molecular sieve as well as a synthesis method and application thereof, and belongs to the technical field of molecular sieves. The anhydrous chemical composition of the molecular sieve is m DMIPA. (Si < x > Al < y > P < z >) O < 2 >, wherein the DMIPA is N, N-dimethyl isopropylamine, and the DMIPA is N, N-dimethyl isopropylamine; m is the mole number of DMIPA in each mole of (Si < x > Al < y > P < z >) O < 2 >, and m is equal to 0.05 to 0.3; x represents the mole fraction of Si, x = 0.05-0.35, y represents the mole fraction of Al, y = 0.35-0.55, z represents the mole fraction of P, z = 0.25-0.45, and x + y + z = 1. The synthesized silicoaluminophosphate molecular sieve SAPO-35 can be used as a catalyst for an acid catalytic reaction, such as a methanol to olefin (MTO) catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieves, and in particular to a SAPO-35 molecular sieve and a synthesis method and application thereof. Background Art

[0002] Silicoaluminophosphate molecular sieve (SAPO-n) is an important type of inorganic microporous material with important application value in the fields of gas adsorption, separation and industrial catalysis. Among the 255 existing molecular sieve topologies, there are more than 40 types of structures composed of silicoaluminophosphate. Compared with silica-alumino molecular sieves of the same topology, SAPO molecular sieves have more suitable and adjustable acidity and good hydrothermal stability, which has attracted widespread attention from researchers in recent years.

[0003] SAPO-35 (LEV topology) is one of the important SAPO molecular sieves. This small pore material It is composed of LEV cages connected by single six-membered rings (S6R) and double six-membered rings (D6R). Its suitable pore structure shows excellent performance in the fields of catalysis and gas adsorption separation.

[0004] SAPO-35 molecular sieves are usually synthesized by hydrothermal method. At present, the template used for synthesizing SAPO-35 molecular sieves is mainly hexamethyleneimine (J.Catal.2017,352,191), in addition to cyclohexylamine, choline cation, N-methyldiethanolamine, 1-methyl-4-piperidinol (Cryst.Res.Technol.1993,28,1101), N-methylpiperidine (Natl.Sci.Rev.2022,9,nwac094), etc. The selection of structure-directing agent will affect the microstructure, elemental composition, chemical environment distribution and crystal morphology of the synthesized molecular sieve products, and thus affect its chemical properties. Therefore, the development of new templates to synthesize SAPO-35 molecular sieves is crucial to regulating its catalytic and adsorption separation properties. Summary of the invention

[0005] In view of this, the present invention provides a SAPO-35 molecular sieve and a synthesis method and application thereof, the main purpose of which is to provide a new synthesis method for synthesizing SAPO-35 molecular sieve so as to easily regulate the crystal morphology, composition and performance.

[0006] In one aspect, the present invention provides a SAPO-35 molecular sieve, wherein the anhydrous chemical composition of the molecular sieve is: mDMIPA·(Si x Al y P z )O2;

[0007] Wherein, the DMIPA is N,N-dimethylisopropylamine;

[0008] m is per mole (Si x Al y P z ) The number of moles of DMIPA in O2, m = 0.05 to 0.3;

[0009] x represents the molar fraction of Si, x = 0.05 to 0.35,

[0010] y represents the molar fraction of Al, y = 0.35 to 0.55,

[0011] z represents the molar fraction of P, z=0.25-0.45, and x+y+z=1.

[0012] Optionally, x is selected from any value among 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, or any range therebetween.

[0013] Optionally, y is selected from any value among 0.35, 0.40, 0.45, 0.50, 0.55, or any range therebetween.

[0014] Optionally, z is selected from any value among 0.25, 0.30, 0.35, 0.40, 0.45, or any range therebetween.

[0015] Optionally, the X-ray diffraction spectrum of the SAPO-35 molecular sieve includes X-ray diffraction peaks at least at the positions shown in the following table:

[0016] No. 2θ 1 8.64 2 10.93 3 11.59 4 13.41 5 17.31 6 17.76 7 20.91 8 21.98 9 23.33 10 27.01 11 28.41 12 32.27 .

[0017] In a second aspect, the present invention provides a method for preparing the above-mentioned nano high-silicon SAPO-35 molecular sieve, comprising the following steps:

[0018] S1: deionized water, silicon source, aluminum source, phosphorus source and N,N-dimethylisopropylamine are mixed to obtain an initial gel mixture;

[0019] S2: The initial gel mixture is subjected to a hydrothermal reaction under sealed conditions, and the product after complete crystallization is separated, washed, and dried to obtain a nano-high-silicon SAPO-35 molecular sieve.

[0020] Optionally, in step S1, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the phosphorus source is calculated as P2O5, and the molar ratio of the components is:

[0021] SiO2 / Al2O3=0-1.5;

[0022] P2O5 / Al2O3=0.5-1.5;

[0023] H2O / Al2O3=10-200;

[0024] DMIPA / Al2O3=0.5~8; DMIPA is N,N-dimethylisopropylamine.

[0025] Optionally, DMIPA / Al2O3=1.0-5; preferably 1.3-3.0.

[0026] Optionally, H2O / Al2O3=20-200; preferably 20-100, further preferably 30-80.

[0027] Optionally, SiO2 / Al2O3 is selected from any value among 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or any range between two values; preferably 0.1 to 1.0.

[0028] Optionally, P2O5 / Al2O3 is selected from any value among 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or any range therebetween.

[0029] Optionally, H2O / Al2O3 is selected from any value of 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 or any range therebetween.

[0030] Optionally, DMIPA / Al2O3 is selected from any value among 0.5, 1, 1.5, 2.0, 2.5, 3.0, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8 or any range therebetween.

[0031] Optionally, in step S2, the temperature of the hydrothermal reaction is 130-220° C., and the crystallization is carried out under autogenous pressure for 5-72 hours.

[0032] Optionally, the temperature of the hydrothermal reaction is selected from any value of 130, 140, 150, 160, 170, 180, 190, 200, 210, 220°C or any range between two thereof; preferably 140-220°C, further preferably 160-200°C.

[0033] Optionally, the crystallization time is selected from any value of 5, 7, 10, 13, 15, 18, 20, 22, 25, 28, 30, 35, 40, 45, 50, 55, 60, 65, 70, 72 hours or any range between two thereof; preferably 20 to 48 hours.

[0034] Optionally, in step S1, the aluminum source is selected from at least one of aluminum nitrate, activated alumina, aluminum hydroxide, aluminum isopropoxide and pseudo-boehmite;

[0035] Preferably, in step S1, the phosphorus source is selected from at least one of orthophosphoric acid, ammonium hydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, diethyl trichloromethylphosphonate and phosphorus-containing oxides;

[0036] Preferably, in step S1, the silicon source is selected from at least one of organosilicon, amorphous silicon dioxide, silica sol, white carbon black, silica gel, diatomaceous earth and water glass.

[0037] Optionally, in step S3, the crystallization process is performed in a static or dynamic state.

[0038] In a third aspect, the present invention provides an acid catalyst, wherein the product obtained by calcining the SAPO-35 molecular sieve or the SAPO-35 molecular sieve prepared by the above preparation method in air at 400-800°C is the acid catalyst.

[0039] In a fourth aspect, the present invention provides a catalyst for the conversion of oxygen-containing compounds to olefins. The product obtained by calcining the SAPO-35 molecular sieve or the SAPO-35 molecular sieve prepared by the above preparation method in air at 400-800°C is the acid catalyst.

[0040] In a fifth aspect, the present invention provides the use of the SAPO-35 molecular sieve or the SAPO-35 molecular sieve prepared by the above preparation method or the above acid catalyst in the reaction of converting oxygen-containing compounds to olefins.

[0041] In a sixth aspect, the present invention provides a method for preparing olefins from methanol, the method comprising: after calcining the catalyst, loading it into a reactor and activating it with nitrogen at 500-600°C for 0.5-1.5h, and reacting methanol at 400-500°C to generate olefins; the catalyst is the above-mentioned nanoscale catalyst.

[0042] In the seventh aspect, the present invention provides a method for preparing methanol to olefins, the method comprising: after the molecular sieve is crushed, air is introduced at a temperature of 550-650°C for calcination for 2-6 hours, the calcined molecular sieve is loaded into a reactor as a catalyst, activated by nitrogen at 500-600°C for 0.5-1.5 hours, and then the temperature is reduced to 400-500°C, the reaction raw material methanol is carried by nitrogen, and olefins are generated by reaction; the molecular sieve is the above-mentioned SAPO-35 molecular sieve or the SAPO-35 molecular sieve prepared by the above-mentioned preparation method.

[0043] Compared with the prior art, the present invention has the following technical effects:

[0044] (1) The present invention provides a SAPO-35 molecular sieve containing N,N-dimethylisopropylamine.

[0045] (2) The present invention provides a method for synthesizing SAPO-35 molecular sieve, which has a simple process, is easy to operate, and is suitable for large-scale industrial production.

[0046] (3) The SAPO-35 molecular sieve prepared by the present invention exhibits excellent catalytic performance in the reaction of converting methanol or dimethyl ether into light olefins. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is the X-ray diffraction spectrum of the SAPO-35 sample prepared in Example 2 of the present invention;

[0048] Figure 2 This is a scanning electron microscope photograph of the SAPO-35 sample prepared in Example 1 of the present invention;

[0049] Figure 3 The SAPO-35 sample prepared in Example 3 of the present invention 13 C solid state NMR spectrum. DETAILED DESCRIPTION

[0050] The present invention will be further described below in conjunction with examples, but the present invention is not limited to these examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods without specifying specific conditions in the following examples are usually based on conventional conditions or according to the conditions recommended by the manufacturer. Without special instructions, the raw materials used in this application are all purchased through commercial channels and are directly used without special treatment.

[0051] The analysis method in the examples of this application is as follows:

[0052] X-ray powder diffraction phase analysis (XRD) was performed using an X'Pert PRO X-ray diffractometer from PANalytical of the Netherlands, with a Cu target, a Kα radiation source (λ=0.15418 nm), a voltage of 40 kV, and a current of 40 mA.

[0053] The instrument used for scanning electron microscopy (SEM) testing is Hitachi SU8020 field emission scanning electron microscope with an accelerating voltage of 2 kV.

[0054] The bulk element composition in the examples was determined using a Magix 2424 X-ray fluorescence analyzer (XRF) from Philips.

[0055] The NMR of the samples was measured using a Bruker Avance III 600 (14.1 Tesla) spectrometer. 13 The resonance frequency of C is 150.9 MHz. 13 C MAS NMR experiments were performed with a 4 mm triple resonance probe, a contact time of 3 ms, an experimental rotation speed of 12 kHz, a sampling delay of 2 s, and adamantane as a chemical shift reference for calibration to 0 ppm.

[0056] Example 1-7 (Synthesis of SAPO-35 Molecular Sieve)

[0057] The synthesis method and results of SAPO-35 are shown in Table 1; first, the aluminum source is mixed and dissolved with water, and then the optional phosphorus source, silicon source and N,N-dimethylisopropylamine (R) are added thereto in sequence. After stirring evenly at room temperature, the gel is transferred to a stainless steel reactor. After the reactor is placed in an oven, the temperature is raised to 140-220°C and reacted for a certain period of time, then the temperature is lowered and crystallization is completed. The solid product is centrifuged, washed, and dried in air at 120°C to obtain a molecular sieve raw powder sample. The synthesized samples are analyzed by XRD, SEM and XRF.

[0058] Table 1 Synthesis conditions and results of molecular sieves 1-7

[0059]

[0060] The seven samples prepared in Examples 1 to 7 were analyzed for phase, morphology and composition:

[0061] The samples of Examples 1-7 were characterized by XRD powder diffraction, and the results showed that they all had characteristic diffraction peaks of SAPO-35, proving that they were LEV crystal phases. Taking Example 2 as an example, the XRD diffraction spectrum of the obtained sample is as follows: Figure 1 1. The peak positions and shapes of the XRD spectra of samples 3-7 are the same as those of Example 2, except that the peak intensity fluctuates by about 10%.

[0062] XRF was used to analyze the inorganic composition of samples 1-7. The results are shown in Table 1, which are: Al 0.47 Si 0.16 P 0.37 O2、Al 0.46 Si 0.20 P 0.34 O2、Al 0.49 Si 0.13 P 0.38 O2、Al 0.46 Si 0.13 P 0.41 O2、Al 0.49 Si 0.04 P 0.47O2、Al 0.49 Si 0.07 P 0.44 O2、Al 0.50 Si 0.07 P 0.43 O2.

[0063] The synthesized samples 1-7 were analyzed by SEM, and the morphology showed similar micron-sized prismatic crystals. Taking Example 1 as an example, its SEM photo is shown in Figure 2 The samples of Example 3 were 13 CMAS NMR solid state nuclear magnetic analysis, such as Figure 3 As shown, it is confirmed that the characteristic peak of N,N-dimethylisopropylamine does exist in the sample.

[0064] Table 2. X-ray diffraction peak data of SAPO-35-2 of Example 2

[0065] No. 2θ 1 8.64 2 10.93 3 11.59 4 13.41 5 17.31 6 17.76 7 20.91 8 21.98 9 23.33 10 27.01 11 28.41 12 32.27

[0066] Application Example 1 (MTO catalytic reaction)

[0067] The low silicon content SAPO-35-6 molecular sieve prepared in Example 6 was first tableted and crushed to 20-40 mesh, and then calcined at 600°C for 4 hours in air; 0.3 g of the sample was loaded into a fixed bed reactor (self-made) as a catalyst for MTO reaction evaluation, and the reactor was a quartz tube; nitrogen was activated at 550°C for 1 hour, and then the temperature was lowered to 450°C for reaction; methanol was carried by nitrogen, and the methanol space velocity was 2h -1 The reaction products were analyzed by online gas chromatography (Agilent A7890) with a PoraPlot-Q-HT column. The results are shown in Table 3.

[0068] Table 3. MTO catalytic performance of synthesized samples a

[0069]

[0070] a Reaction conditions: 450°C, methanol space velocity 2h -1 ; Lifetime is defined as the length of time when methanol conversion is greater than 99%, and selectivity gives the result when ethylene plus propylene selectivity is highest.

[0071] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A SAPO-35 molecular sieve, characterized in that: The anhydrous chemical composition of the molecular sieve is: mDMIPA·(Si x Al y P z )O2; Wherein, the DMIPA is N,N-dimethylisopropylamine; m is per mole (Si x Al y P z ) The number of moles of DMIPA in O2, m = 0.05 to 0.3; x represents the molar fraction of Si, x = 0.05 to 0.35, y represents the molar fraction of Al, y = 0.35 to 0.55, z represents the molar fraction of P, z=0.25-0.45, and x+y+z=1.

2. A SAPO-35 molecular sieve according to claim 1, characterized in that: The X-ray diffraction spectrum of the SAPO-35 molecular sieve includes X-ray diffraction peaks at least at the positions shown in the following table: 。 3. The method for preparing a SAPO-35 molecular sieve according to any one of claims 1 to 2, characterized in that: The preparation method comprises the following steps: S1: deionized water, silicon source, aluminum source, phosphorus source and N,N-dimethylisopropylamine are mixed to obtain an initial gel mixture; S2: The initial gel mixture is subjected to a hydrothermal reaction under sealed conditions, and the product after complete crystallization is separated, washed, and dried to obtain a nano-high-silicon SAPO-35 molecular sieve.

4. The method for preparing a SAPO-35 molecular sieve according to claim 3, characterized in that: In step S1, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the phosphorus source is calculated as P2O5, and the molar ratio of the components is: SiO2 / Al2O3=0-1.5; P2O5 / Al2O3=0.5-1.5; H2O / Al2O3=10-200; DMIPA / Al2O3=0.5~8; DMIPA is N,N-dimethylisopropylamine.

5. The method for preparing a SAPO-35 molecular sieve according to claim 4, characterized in that: DMIPA / Al2O3=1.0~5; H2O / Al2O3=20~200; Preferably, DMIPA / Al2O3=1.3-3.0; H2O / Al2O3=20-80; Preferably, in step S2, the temperature of the hydrothermal reaction is 130-220° C., and the crystallization is carried out under autogenous pressure for 5-72 hours; Preferably, the temperature of the hydrothermal reaction is 140-220°C; Preferably, the temperature of the hydrothermal reaction is 160-200°C.

6. The method for preparing a SAPO-35 molecular sieve according to claim 4, characterized in that: In step S1, the aluminum source is selected from at least one of aluminum nitrate, activated alumina, aluminum hydroxide, aluminum isopropoxide and pseudo-boehmite; Preferably, in step S1, the phosphorus source is selected from at least one of orthophosphoric acid, ammonium hydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, diethyl trichloromethylphosphonate and phosphorus-containing oxides; Preferably, in step S1, the silicon source is selected from at least one of organosilicon, amorphous silicon dioxide, silica sol, white carbon black, silica gel, diatomaceous earth and water glass.

7. The method for preparing a SAPO-35 molecular sieve according to claim 3, characterized in that: In step S1, the crystallization process is performed in a static or dynamic state.

8. An acid catalyst, characterized in that The product obtained by calcining the SAPO-35 molecular sieve described in any one of claims 1 to 2 or the SAPO-35 molecular sieve prepared by the preparation method described in any one of claims 3 to 7 in air at 400 to 800° C. is the acid catalyst.

9. Use of the SAPO-35 molecular sieve according to any one of claims 1 to 2, or the SAPO-35 molecular sieve prepared by the preparation method according to any one of claims 3 to 7, or the acid catalyst according to claim 8 in the reaction of converting oxygen-containing compounds to olefins.

10. A method for preparing olefins from methanol, characterized in that: The method comprises: after the molecular sieve is crushed, air is introduced into the molecular sieve for calcination at a temperature of 550 to 650° C. for 2 to 6 hours, the calcined molecular sieve is loaded into a reactor as a catalyst, nitrogen is introduced for activation at 500 to 600° C. for 0.5 to 1.5 hours, and then the temperature is lowered to 400 to 500° C., and the reaction raw material methanol is carried by the nitrogen to react to generate olefins; the molecular sieve is the SAPO-35 molecular sieve described in any one of claims 1 to 2 or the SAPO-35 molecular sieve prepared by the preparation method described in any one of claims 3 to 7.

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